Resistant Prions: Can They Be Transmitted By Environment As Well As Direct Contact?

[n2doc]

ScienceDaily (Aug. 16, 2008) — Prions, the pathogens that cause scrapie in sheep, can survive in the ground for several years, as researchers have discovered. Animals can become infected via contaminated pastures. It is not yet known whether the pathogens that cause BSE and CWD are equally resistant.

A flock of sheep at pasture – a seemingly idyllic scene. But appearances can be deceptive: If the animals are suffering from scrapie, entire flocks may perish. Scrapie is an infectious disease in which prions destroy the animal’s brain, rather like BSE. The brain becomes porous, the sheep lose their orientation, they suffer from strong itching sensations and scrape off their fleece. Eventually, the infected animals die.
It is difficult to contain the disease – all too often, scrapie will break out again on the same farm several months or years after it has apparently been eradicated. Are the prions transmitted not only by direct contact, but also by the environment – perhaps by the pastures? How long do prions that get into the pasture via the saliva and excrements of the sick animals, persist in the ground?

Together with fellow-scientists from the Robert Koch Institute in Berlin and the Friedrich Loeffler Institute (Federal Research Institute for Animal Health) on the island of Riems, research scientists from the Fraunhofer Institute for Molecular Biology and Applied Ecology IME in Schmallenberg investigated these questions on behalf of the German Ministry for Environment, Nature Conservation and Nuclear Safety BMU.
“We mixed soil samples with scrapie pathogens to find out how long the pathogens would survive,” says Dr. Björn Seidel, who headed the investigations at IME. “Even after 29 months, in other words more than two years, we were still able to detect prions in the soil.”

But are these prions still infectious? “The soil actually seems to increase the infectiousness of the pathogens. The incubation period – the time it takes for the disease to break out – is exceedingly short even after the prions have persisted in the soil for 29 months. All of the animals that were given contaminated soil became sick within a very short time. These results indicate that fresh incidences of scrapie among sheep are due to contaminated pastures,” says Seidel in summary.

more:
http://www.sciencedaily.com/releases/2008/08/080811095458.htm

[Ian David]

1. We're all just going to wake up sick one day and start dying. The vegitarians, too.

Who knows if the farmland used to grow the soy for their tofurkey is infected with prions?

[kestrel91316]

2. I've heard they are resistant to enzymatic degradation. Scary.

Also, ask any neurosurgeon if they use disposable equipment vs reusable in surgery, and why.

[sam sarrha]

3. here is a link>>

http://www.maddeer.org

%3BS%3Ahttp%3A%2F%2Fwww.organicconsumers.org%3BFORID%3A1&hl=en

http://www.fortunecity.com/healthclub/cpr/798/cjd.htm

death list of infected people
http://www.fortunecity.com/healthclub/cpr/349/index.html

independent researcher on NPR said tests done in Alzheimer's wards showed that 13% of patients were misdiagnosed CJD cases
http://www.mad-cow.org/Alzheimer_cjd.html

http://spyglasshill.com/Articles/detail.asp?iData=125&iCat=296&iChannel=2&nChannel=Articles
With very few autopsies being done on people diagnosed as having Alzheimer's disease, and <1% of the cattle being tested for Mad Cow, how do we know we don't really have an outbreak of Mad Cow or similar variants like CJD? This research documents autopsies done on people diagnosed with Alzheimer's to see how accurate that diagnosis was. The results are alarming.

list http://www.google.com/search?hl=en&sa=X&oi=spell&resnum=0&ct=result&cd=1&q=alzheimer%27s+misdiagnosed+cjd&spell=1

[azul]

5. What did the Mars lander find?

Prions. (I presume I'm kidding.)

Thanks for the links. But they are rather dated. Have you noticed the dearth of newer information? Is there a presidential or other constraint on such research and publication, or just funding shortages? Alar laws?

The US beef industry touts a zero chance of getting BSE from today's herd. Why then the riots in S Korea?

[DemBones DemBones]

4. I wish the article had made it clear HOW the sheep

were "given" contaminated soil. Was it simply put in their pasture or was it actually fed to them? Presumably sheep ingest some soil while grazing.

It's bad news for sheep farmers with scrapie in their flocks because it means it could be several years before pasture used by those sheep is safe for sheep again.



"The results of the study reveal that sheep may even become infected from the surface water, though the risk of infection is much lower in this case. There is no danger to humans, however: scrapie pathogens seem unable to affect them."

"Another cause for concern is chronic wasting disease (CWD). Like BSE and scrapie, this is caused by prions, but it mainly affects deer. The numbers of infected animals in North America are rising steeply. How long do BSE and CWD prions survive in the ground? “To find this out, we urgently need to carry out further tests. The appropriate research applications have already been submitted,” says Seidel."



I hope the research for survival of BSE and CWD prions is funded promptly since it will take years to know the results. They need to keep studying scrapie as well because it may be that they just haven't seen transmission to humans yet.

I found a CDC article about CWD, which seems to have crossed the species barrier to humans as BSE did.


http://www.cdc.gov/NCIDOD/EID/vol10no6/03-1082.htm

"Chronic wasting disease (CWD) is classified as a transmissible spongiform encephalopathy (TSE), or prion disease, along with other animal diseases, such as scrapie and bovine spongiform encephalopathy. The only known natural hosts for CWD are deer (Odocoileus species) and Rocky Mountain elk (Cervus elaphus nelsoni) (1,2). CWD and other TSEs are believed to be caused by a pathogenic effect on neurons of an abnormal isoform of a host-encoded glycoprotein, the prion protein. The pathogenic form of this protein appears to be devoid of nucleic acids and supports its own amplification in the host. TSEs in animals primarily occur by transmitting the etiologic agent within a species, either naturally or through domestic husbandry practices. In contrast, most such encephalopathies in humans occur as a sporadic disease with no identifiable source of infection or as a familial disease linked with mutations of the prion protein gene (3). A notable exception among the human TSEs is the variant form of Creutzfeldt-Jakob disease (vCJD), which is believed to have resulted from the foodborne transmission of bovine spongiform encephalopathy (BSE) to humans."

<snip; lots of case histories about vCJD in humans, info about animals that have CWD and where they are, etc.
>

"The lack of evidence of a link between CWD transmission and unusual cases of CJD, despite several epidemiologic investigations, and the absence of an increase in CJD incidence in Colorado and Wyoming suggest that the risk, if any, of transmission of CWD to humans is low. Although the in vitro studies indicating inefficient conversion of human prion protein by CWD-associated prions raise the possibility of low-level transmission of CWD to humans, no human cases of prion disease with strong evidence of a link with CWD have been identified. However, the transmission of BSE to humans and the resulting vCJD indicate that, provided sufficient exposure, the species barrier may not completely protect humans from animal prion diseases. Because CWD has occurred in a limited geographic area for decades, an adequate number of people may not have been exposed to the CWD agent to result in a clinically recognizable human disease. The level and frequency of human exposure to the CWD agent may increase with the spread of CWD in the United States. Because the number of studies seeking evidence for CWD transmission to humans is limited, more epidemiologic and laboratory studies should be conducted to monitor the possibility of such transmissions."


Oddly enough, I could swear a U.S. forest manager told me about CWD occurring in deer here in my area more than twenty years ago, and I'm far from the areas identified in this article from the CDC, dated four years ago. Maybe he was just talking about fearing it would spread here, where we have too many deer and they are not growing to full size unless they have a good mast year. They trap a lot of them and transport them to other areas of the state but the population is out of control and they've lost their fear of humans.

[pipoman]

6. CWD has been around for a very long time

the disease could be magnified by over population. Another reason deer culling is important for the health and survival of the wild deer populations.